Undesirable growth of animal and plant life on submerged surfaces results in major costs to the shipping industry, aquaculture and any other industries that relies on equipment submerged in a marine or freshwater environment. This marine growth, known as fouling, can seriously diminish the performance of a ship's hull through the water, as well as causing structural damage. Both marine and freshwater vessels are susceptible to bottom fouling that can result in significant economic penalties.
Aquaculture is the business of the regulation and cultivation of water plants and animals for human use or consumption. Typically, there is a rapid build up of marine fouling on the structures used in aquaculture such as, ropes, nets, buoys, cages and traps, which is costing the industry billions of dollars annually through labor intense maintenance to clean these materials. Aquaculture is an industry that produces at least 50 billion dollars per year globally and there is not a known environmentally safe antifouling coating for aquaculture systems. As a result the industry loses approximately 3 to 5 billion dollars per year in lost production due to the results of fouling. Another 1 billion dollars per year is spent on the manual cleaning of these systems.
Historically, toxic chemicals including heavy metals and their salts have been added to marine paints to control the build up of organisms on vessel hull bottoms and structures. Two chemicals, tributyltin (TBT) and cuprous oxide (copper) have been in commercial use for decades as antifouling agents in marine paints. However, tributylin is now banned worldwide due to its high toxicity to free-floating marine organisms when leached into the surrounding water. Cuprous oxide is also of concern because of the build-up of high concentrations of copper ions in harbor sediment, again after leaching from the anti-fouling coatings.
Both chemicals, therefore, have a detrimental impact on the marine environment worldwide and replacements are eagerly sought. However, attempts to replace the current toxic chemicals with alternatives that are non-toxic when released into the surrounding water, or mechanical alternatives that could dislodge attaching marine growths, have met with limited success. Furthermore, neither tributyltin (TBT) nor cuprous oxide can be used in the aquaculture industry that requires agents that will not adversely affect the growth of the farmed fish themselves and which do not provide danger to the ultimate consumer. Antifouling coatings, including such as marine paints, typically comprise combinations of binders, pigments, additives and solvents. The binders determine the characteristics of the antifouling, including leaching of biocidal components into the surrounding water. Pigments include the antifouling toxic agent(s) and various fillers. The solvents provide the application properties, while the additives are stabilizers for extended shelf life and to prolong the efficacy of the paint or coating once applied to the ship surface.
The three classes of antifouling paints currently in use are leaching (hard and soft), ablative coatings and self-polishing coatings (polymers). Leaching (hard and soft) is the process whereby the toxicant comes out of the paint at a controlled and sustained rate. Ablative coatings comprise a soluble matrix in the coating (film) that is made up of the natural product rosin and hydrocarbons that act as a binder in the soluble matrix. Self-polishing antifoulings are of two types, those containing tin (TBT) and those that are tin-free.
Non-toxic and self-polishing polymer coatings such as silicones, TEFLON™ and epoxies are coatings that have offered possible alternatives to marine paints containing toxic antifouling agents, but have found little or no use in the aquaculture industry. Because of the slick surface marine microorganisms have a difficult time attaching. However, these non-toxic coatings would be further enhanced with the addition of environmentally benign phytochemical-based antifouling compositions.
Non-marine structural surfaces may be also subject to undesirable biocontamination. For example, in buildings where high humidity and temperature are encountered, mildew, fungi or bacterial growth are encouraged that can release airborne allergens and cause asthma and other ailments. Medical facility surfaces demand substantially reduced level of contaminating level of microbial colonization, usually achieved by disinfection, to avoid nosocomial infections. If persons or animals are to come into direct contact with architectural or other surfaces, it is desirable that active biocidal compounds that may be incorporated in the protective coatings be both long lasting and present minimal environmental hazards.
There is still an existing need, however, for effective and economical antifouling coatings that may allow the aquaculture industry to reduce the labor intense problem of cleaning fouling from aqua culture equipment or which do not present an environmental danger when applied to ship hulls. Phytochemicals are known which have broad activity, preventing or inhibiting the growth of a broad spectrum of microbes, as well as exhibiting efficacy against a range of potentially marine fouling organisms such as barnacles and algae. For example, biocidal phytochemicals have been incorporated into polymeric films useful for wrapping and protecting foodstuffs during storage as (see, e.g., U.S. Pat. No. 5,906,825). Capsicum, at high pungency levels, has been added to marine paints to prevent the fouling of ships bottoms (see, e.g., U.S. Pat. No. 5,397,385). Furanones from marine algal sources have been incorporated into coatings of aquaculture equipment (see, e.g., U.S. Pat. Nos. 6,692,557, 6,635,692 and 6,060,046).
Phytochemicals that leach out of paint dilute and disperse extremely well into water and their biodegradability ensures they do not accumulate to unacceptable levels in the environment. Their antifouling effect particularly resides in a surface effect that takes place only in the immediate environment of the painted or coated surface. This characteristic makes the compositions of the present invention comprising phytochemicals compatible with UHMW polyethylene and VHMW polyethylene, silicones and latex compounds.
A need still exists, however, for a safe, environmentally friendly alternative to toxic additives in marine paints and architectural coatings, which does not comprise a highly pungent level of capsicum that may be harmful to the applicant of the paint and to individuals who may come into direct contact with a treated surface.
Citation or identification of any document in this application is not an admission that such document is available as prior art to the present invention.